1. Field of the Invention
The present invention relates generally to methods and apparatus for improving the heating performance and productivity of glass melting furnaces and the like. More particularly, the present invention relates to the use of oxygen lances that are installed though holes in furnace walls to inject flows of oxygen in directions that extend substantially parallel to the top surface of a bath of molten glass contained within the furnace. The injected flows extend in closely spaced relationship to the top surface of the molten glass (l) to draw a blanket of flame from a location spaced above the glass downwardly into contact with the glass, and (2) to improve combustion and flame coverage in selected areas of the furnace, to concurrently improve flame positioning and character, whereby improvements also result in heat transfer from the combustion zone to the molten glass, and combustion efficiency within the combustion zone.
2. Prior Art
In a glass melting furnace, a large melting tank typically is defined at least in part by wall structures that are thick and provide only limited access to contents within the melting tank. Constituents used to manufacture glass are introduced into the tank and heated therein to provide a bath of molten glass. As some of the molten glass is withdrawn from the bath for use in manufacturing processes, additional ingredients are added to the bath to replenish the bath and to keep its top surface at a substantially constant level.
Contents of the melting tank or "basin" of the furnace are heated, at least in part, by using an array of nozzles that inject natural gas (or other fuel) downwardly toward and transversely across the top surface of the molten glass to form what can be thought of as a "blanket" of flame that extends over a major portion of the bath of molten glass. To maximize productivity and to minimize fuel waste, it is desirable to obtain relatively uniform flame coverage over the area of the furnace basin, and to feed fuel and oxygen to the combustion zone in such a way that complete combustion of the fuel is achieved.
However, a problem inherent in operating a furnace of this type is that, depending on a wide variety of factors that vary from location to location across the top of the furnace basin, the character of the flame blanket that results a combustion is used to heat molten glass is found to differ in a variety of ways including such characteristics as flame character, flame spread, uniformity of flame coverage, combustion efficiency, heat transfer rate and efficiency, etc. Factors that cause such variations may include the character of the supply of natural gas and/or combustion air to a particular region, whether conduits and/or nozzles are fully operational, partially obstructed, deformed and/or deteriorated in character, etc. But, regardless of the reason or reasons for nonuniformity of flame blanket composition and character, it is desirable from the point of view of heating the glass efficiently that some means be provided to improve flame character and heating performance. While the need for an effective means to provide localized improvement extends throughout the combustion zone, it is especially prevalent in areas over the furnace basin where deficiencies in the character of the flame blanket are found to be quite pronounced.
Another problem has to do with the height at which the blanket of flame tends to reside above the upper surface of the bath of molten glass. The tendency of the flame blanket to reside at a distance spaced above the top surface of the molten glass may result from the interaction of a number of factors including the presence of upwardly moving flows of hot gases that emanate from the bath, the paucity of oxygen in the combustion zone layer that resides immediately adjacent the top surface of the bath, etc. But, regardless of the reason or reasons that may explain why the flame blanket tends to reside at a location spaced above the molten glass, there can be no disputing the desirability of providing a suitable method and means for forcing the flame blanket downwardly to enhance flame positioning and coverage, and to thereby improve the efficiency of the flame blanket in heating the molten glass.
Still another problem is that of enhancing and maintaining good combustion efficiency. While this problem has been addressed by a wide variety of proposals including the proposed use of devices of various types for injecting oxygen at discrete burner locations to treat the flame patterns within combustion zone areas that are served by selected burners, the need remains for a relatively simple and inexpensive system that is adequately flexible to address the complex needs of a combustion zone in a glass melting furnace as by providing localized enhancement of combustion as by the controlled injection of oxygen.